module TitleCase (titleCase) where

import qualified Data.Char as Char

titleCase :: String -> String -> String
titleCase minor title =
  unwords $
    map toTitle (take 1 titleWords)
    <> map maybeToTitle (drop 1 titleWords)
  where
    titleWords, minorWords :: [String]
    titleWords = words . toLower $ title
    minorWords = words . toLower $ minor

    maybeToTitle :: String -> String
    maybeToTitle word
      | word `elem` minorWords = word
      | otherwise              = toTitle word

toTitle :: String -> String
toTitle t = case t of
  ""     -> ""
  (x:xs) -> Char.toUpper x : xs

toLower :: String -> String
toLower = map Char.toLower